Chapter 31
Plant reproduction and growth
Plant growth
Fig 31.7
Plant growth
• Plants have indeterminate growth
• Annuals, biennials, periannials
• Meristems
– Apical; grows at tips of shoots and roots
• Gives rise to cortex, epidermis, and vascular tissues
• Primary growth lenghtens shoots and roots
• Secondary Growth (from cambium)
Primary growth
Fig 31.7
Secondary Growth
Fig 31.8A
Secondary Growth
• Increases girth of woody plants
– Meristems that grow laterally
– Vascular cambium; develops from parenchyma
between xylem and phloem
– Outer layers (older) slough off as bark
– Cork cambium; produces layers of cork that
protect the plant
Anatomy of a log
Fig 31.8B
Anatomy of a log
• Heartwood; xylem plugged with resins, acts
as an endoskeleton
• Sapwood; secondary xylem that conducts
water
Sexual lifecycle in Angiosperms
Fig 31.9
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Sexual lifecycle in Angiosperms
• Flowers; compressed shoots with modified
leaves
– Sepals; green, protect flowers
– Petals; colorful, attract pollinators
– stamens; male, have anthers at tip, deliver
pollen
– carpels+ female, stigma, style ,ovule bear
ovules
– What is pollination?
• Monocots and eudicots differ in seed leaf
number and in the structure of roots, stems,
leaves, and flowers
Angiosperms
Ovule to Seed
Fig 31.11
Seed development
• Triploid cell- develops into endosperm
• Zygote develops into embryo
• Ovule coat develops into the seed coat
Seed Structure
Fig 31.11
Seed Germination
31.13
Previously developing embryo starts again
after dormancy
Seed takes up water, expands, ruptures its
coat, stored nutrients are broken down
and fuel growth
Fruit Development
Fig 31.12
Fruits
• Houses, protects, disperses seeds
• Types of fruits
– Simple; pea pod (single carpel and
ovary)
– Aggregate; blackberry (many carpels)
– Multiple; pineapple (many flowers)
Plant Cells
•
•
•
•
Two part cell wall
Stiff secondary cell wall
Middle lamellae
Plasmodesmata
31.5 Plant cells and tissues are
diverse in structure and function
Figure 31.5A
• There are five major types of plant cells
–
–
–
–
–
Parenchyma
Collenchyma
Sclerenchyma
Water-conducting cells
Food-conducting cells
• Parenchyma cells function in food storage,
photosynthesis, and aerobic respiration
• Thin primary cell walls
Primary
wall
(thin)
Pit
Figure 31.5B
• Collenchyma cells provide support in parts of the
plant that are still growing
• Unevenly thickened primary cell walls
Figure 31.5C
• Sclerenchyma cells provide a rigid scaffold that
supports the plant
– Rigid secondary
cell walls
(Lignin)
– Fiber cells
– Sclerid cells
– Sclereids (stone
cells) (gritty pear)
Figure 31.5D
• Water-conducting cells convey water from the
roots to the stems and leaves
– Chains of
tracheids (long
w/tapered ends)
or vessel
elements(shorter
and broader)
form a system of
tubes for water
transport
Pits
Tracheids
Vessel element
Pits
Openings
in end wall
Figure 31.5E
• Food-conducting cells function in the transport of
sugars, other compounds, and some mineral ions
– Sieve-tube members are arranged end-to-end,
forming tubes
– Their end walls are perforated with plasmodesmata,
forming sieve plates
– At least one companion cell flanks each sieve-tube
member
Sieve plate
Companion
cell
Cytoplasm
Primary
wall
Figure 31.5F
• Complex tissues are composed of more than one
type of plant cell
• Vascular tissues are complex tissues that conduct
water and food
– Xylem contains water-conducting cells that convey
water and dissolved minerals
– Phloem contains sieve-tube members that transport
sugars